promise-lesson-1-orders.js

function printString (str) {
  setTimeout(
    console.log,
    Math.floor(Math.random() * 100) + 1,
    str
  )
}

function printAll () {
  printString('A')
  printString('B')
  printString('C')
  printString('D')
  printString('E')
}

// printAll()

/* Callback */

function printStringWithCb (str, cb) {
  setTimeout(
    x => {
      console.log(x)
      cb()
    },
    Math.floor(Math.random() * 100) + 1,
    str
  )
}

function printAllWithCb () {
  printStringWithCb('A', () => {
    printStringWithCb('B', () => {
      printStringWithCb('C', () => {
        printStringWithCb('D', () => {
          printStringWithCb('E', () => {
          })
        })
      })
    })
  })
}

// printAllWithCb()

/* Promise: using the Promise Constructor */

function printStringWithPromise (str) {
  return new Promise((resolve, reject) => {
    setTimeout(
      () => {
        console.log(str)
        resolve()
      },
      Math.floor(Math.random() * 100) + 1,
    )
  })
}

function printAllWithPromise () {
  return printStringWithPromise('A')
    .then(() => printStringWithPromise('B'))
    .then(() => printStringWithPromise('C'))
    .then(() => printStringWithPromise('D'))
    .then(() => printStringWithPromise('E'))
}

// printAllWithPromise()

/* Promise: using the Promisify Util */

function printStringWithPromise2 (str) {
  const util = require('util')
  const setTimeoutPromise = util.promisify(setTimeout)
  return setTimeoutPromise(
    Math.floor(Math.random() * 100) + 1,
    str
  ).then(console.log)
}

function printAllWithPromise2 () {
  return printStringWithPromise2('A')
    .then(() => printStringWithPromise2('B'))
    .then(() => printStringWithPromise2('C'))
    .then(() => printStringWithPromise2('D'))
    .then(() => printStringWithPromise2('E'))
}

// printAllWithPromise2()

/* Promise with Async/Await */

async function printAllWithAsyncAwait () {
  await printStringWithPromise2('A')
  await printStringWithPromise2('B')
  await printStringWithPromise2('C')
  await printStringWithPromise2('D')
  await printStringWithPromise2('E')
}

printAllWithAsyncAwait()

promise-lesson-2-catch-values.js

/* Callback */

function addStringWithCb (prev, curr, cb) {
  setTimeout(
    () => {
      const result = `${prev} ${curr}`
      cb(result)
    },
    Math.floor(Math.random() * 100) + 1,
  )
}

function printAllWithCb () {
  addStringWithCb('', 'A', result => {
    addStringWithCb(result, 'B', result => {
      addStringWithCb(result, 'C', result => {
        addStringWithCb(result, 'D', result => {
          addStringWithCb(result, 'E', result => {
            console.log(result)
          })
        })
      })
    })
  })
}

printAllWithCb()

/* Promise: using the Promise Constructor */

function addStringWithPromise (prev, curr) {
  return new Promise((resolve, reject) => {
    setTimeout(
      () => {
        const result = `${prev} ${curr}`
        resolve(result)
      },
      Math.floor(Math.random() * 100) + 1,
    )
  })
}

function printAllWithPromise () {
  return addStringWithPromise('', 'A')
    .then(result => addStringWithPromise(result, 'B'))
    .then(result => addStringWithPromise(result, 'C'))
    .then(result => addStringWithPromise(result, 'D'))
    .then(result => addStringWithPromise(result, 'E'))
    .then(console.log)
}

printAllWithPromise()

/* Promise: using the Promisify Util */

function addStringWithPromise2 (prev, curr) {
  const util = require('util')
  const setTimeoutPromise = util.promisify(setTimeout)
  return setTimeoutPromise(
    Math.floor(Math.random() * 100) + 1,
    prev,
  ).then(prev => `${prev} ${curr}`)
}

function printAllWithPromise2 () {
  return addStringWithPromise2('', 'A')
    .then(result => addStringWithPromise2(result, 'B'))
    .then(result => addStringWithPromise2(result, 'C'))
    .then(result => addStringWithPromise2(result, 'D'))
    .then(result => addStringWithPromise2(result, 'E'))
    .then(console.log)
}

printAllWithPromise2()

/* Promise with Async/Await */

async function printAllWithAsyncAwait () {
  let result = ''
  result = await addStringWithPromise2(result, 'A')
  result = await addStringWithPromise2(result, 'B')
  result = await addStringWithPromise2(result, 'C')
  result = await addStringWithPromise2(result, 'D')
  result = await addStringWithPromise2(result, 'E')
  console.log(result)
}

printAllWithAsyncAwait()